Control strategies are vital for rapid temperature changes
27 Nov 2019
Manufacturing processes that rely on rapid temperature change can easily result in bottlenecks in an overall process, warns Bürkert’s Mark Lilley...
Temperature controlled processes are used in a number of manufacturing industries, such as aluminium die casting, injection moulding, extrusion processes and a range of food manufacturing techniques. Precise and consistent control of temperature through accurate heating and cooling is very important in terms of product quality and process efficiency.
These examples demonstrate how a modular process control platform can be used to create a tailored solution for any manufacturing process.
Casting the die
In the manufacture of high pressure die-cast aluminium parts, tool temperatures have a significant influence on surface finish, dimensional accuracy and the amount of finishing required. Also, cost-effective manufacturing requires cycle times and reliability to be optimised, Hence, a need for automated systems with the fastest practical cycle times.
This requires a dynamic control system comprising precision temperature sensors, flow control valves and isolation valves that can reliably manage the fast heating and cooling rates of the thermoregulation process.
Precise and consistent control of temperature through accurate heating and cooling is very important in terms of product quality and process efficiency
A modular process control system can integrate with existing machinery, adding as many sensors and control valves as necessary to deliver an ideal solution regardless of the original manufacturer. With sufficient planning and design expertise, the platform can also provide flexibility in the wider manufacturing process by enabling fast, efficient batch changeovers and adaptation for new lines.
One of the major challenges in injection moulding is to produce parts that fall from the die ready for use.
An important contribution towards achieving this aim is made by vario-thermal control of the injection moulding tool. Only with this technique is it possible to produce plastic parts without distortion, with the right size and with high surface quality regarding gloss, haptic properties and lack of weld lines.
The main temperature regulation challenge is to enable rapid changes between temperatures around 180°C during the injection phase, and cooler temperatures of approximately 100°C. Of course, this should be achieved with low cycle times as far as possible to maintain productivity.
The key is to position the valve switching station close to the tool, so the transition from hot to cooler temperatures involves only a very small exchange of water within the system. In conjunction with accurate temperature measurement and flow control valves it is possible to create a very reliable and efficient process by implementing a modular process control platform. This enables the seamless integration of sensors, flow measurement devices and flow control valves within an existing installation.
Improving profile accuracy
Extrusion technology is used to manufacture a wide range of products using plastics and metals and the overriding objective is to produce a uniform profile without distortion or variation in the dimensions. The decisive factor in achieving this goal is maintaining the correct process temperatures, regardless of external influences.
The cooling process is as important as the heating procedures and as such industrial extrusion equipment will benefit from a modular process control platform. As a complete process temperature regulation system, this solution automates the controlled heating of the extruder sections and targeted cooling in the subsequent calibration stations.
With a flexible layout, each system allows the highest levels of quality to be achieved because the number of cooling points and nozzles can be varied and each one can be equipped with a dedicated, decentralised control unit. By working with expert designers, it is possible to create bespoke temperature control systems that provide the necessary levels of flexibility and reliability.
Mark Lilley is field segment manager, hygienic – food & beverage for Bürkert Fluid Control Systems